The civilization known for its advanced architecture and the construction of ziggurats was the Sumerians, who inhabited ancient Mesopotamia, in present-day Iraq. Ziggurats were massive step pyramid structures built as temples to deities, showcasing the Sumerians' architectural innovation and religious devotion. These structures served as centers of worship and administrative activity. The Sumerians made significant contributions to writing, law, and urban planning, influencing subsequent cultures in the region. They are often credited with establishing one of the earliest known civilizations, with complex social structures and trade networks that laid the foundation for later cultures in Mesopotamia.